Microphone



Sept. 20, 1932. H. J. ELLls 1,878,271

MICROPHONE Filed July '7. 1950 this opening is the sleeve 14. This sleeve 14 is provided with .a central threaded opening 15, within which is the screw for the binding post 16 at the outer end, and the threaded stem of the microphone button mounting 17 at its inner portion. The microphone but# ton 19, made of carbon or other suitable material, is securely attached to the inner end of the mounting' 17. The inner end of the bushing 12 is formed into acup shape extending enclose the microphone button, and part-of the thickness of the felt washer 20 disposed within said cup shaped portion, in contact with the microphone button. Said washer 20 is designed to form a 'recess between the microphone button vand the diaphragm for the reception and retention ofthe carbon granules 21 placed therewithin. The washer 2O is preferably made of lyielding material,

to permit it to be compressed, as thebushing12 is moved rearwardly to compress the carbon granules between the microphone button and the diaphragm. set screw 24 is provided to lock the bushing in any position to which it has been adjusted, against accidental movement from said position.

The forward surface of the rear section2 is provided with a recess at 22 to avoid possibility of the diaphragm coming into contact withrsaid section member at any portion of the stretched central portion thereof. At the middle portion of the rear member 2 is provided a perpendicularly extending hub 23. This hub has a centrally threaded vopening similar to hub 10 in which a bushing similar to 12 is threaded. The bushing in turn has a central opening with a sleeve, binding post, microphone button mounting, button, felt washer and carbon granules all similar to parts 13, 14, 15, 16, 17, 19, 20, 21 above described, and a set screw similar to 24 for the same purpose. Binding post nuts may-be attached to'two ofthe screws 4, 4 ing one of the operative line wires (not shown) and the other line wire may be con# nected to the binding post screws 16, 16.

' To assemble this microphone, theY diaphragm is placed between the sections 1 and 2 with the screwk holes in alignment. Screws 4,' 4 are inserted and screwed down tight to bind the said ldiaphragm firmly between said sections Y1 and 2. The ring25 is next screwed into the forward section 1, and turned'until it engages vthe diaphragm with any tension desirable. Theparts 14, 16, 17, 19, 2O and 21 are properly assembledy witlithe bushing 12, and the bushing is then screwed into thehub secured together granules may be increased, or decreased, to increase or decrease the resistance to the electric current passing therethrough. By these means, the said microphone may be easily and quickly adjusted toany desired resistance, or to any resistance aving thus described my invention, what IClaim, and desire to secure by Letters Patent,'is the following In a device of the class described, the cornbination of a frame composed of two sections by means of screws, a dia- 121 i mounted between said sections, said diaphragm having perforations through Vwhich said screws extend, an annular member adjustableV axially within the frame and Ycontacting said diaphragm Afor stretching the latter, a centrally disposed threaded opening in the frame on each side of said diaphragm, externally threaded bushings of insulated material adjustably mounted in said opening, each of said bushings being recessed-to form a resistor cup, an electrode mounted inthe bottom of each of said resistor cups, a felt washer mounted in each of said resistor cups and in Contact with said diaphragm, carbon granules retained in the central opening in each washer and in contact with thediaphragm, and means for locking said bushings in adjusted position.

In testimony whereof, I have duly signed the foregoing specification.

HUGH J. ELLIS.

iragni rigidly microphone for convenience in attachl 10 until the washer 20'contacts with the dia- 'n Y l phragm. By turning the-ring 25 forward orback the Vtension on the diaphragm may be increased or decreased, asfdesiredfor most etleient service,`and turning the bushings forward' or back, the pressure uponfthe carbon 

